The Integumentary System
Skin, Hair, Nails, and Glands
Do Now:
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Calculate the weight of your skin:
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For average adult skin accounts for 7% of
body weight!
Thickness ranges from 1.5mm –
4.0mm
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Where on the body is it thickest?
Thinnest?
Integumentary Structure
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2 Components:
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Cutaneous Membrane
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Epidermis
Dermis
Hypodermis
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aka subcutaneous layer
Superficial fascia
Accessory Structures
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Hair
Nails
Exocrine Glands
Integumentary Function
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Protection
Temperature
maintenance
Synthesis and
storage of nutrients
Sensory reception
Excretion and
secretion
Epidermis
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Avascular & Keratinized
Thick skin – 5 layers
Thin skin – 4 layers
New epidermis every 25-45 days
Cells:
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Keratinocytes (most cells) – produce keratin
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Melanocytes – (spider shaped) produce melanin
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Tightly connected by desmosomes
Callus – accelerated keratin formation
Melanin taken in by keratinocytes
Shields nucleus from UV
Merkel cells – sense skin curvature
Langerhans’ cells – star shaped phagocytes
Layers of Epidermis
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Layers (starting from basement
membrane):
 Stratum Germinativum (Basale)
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3 Intermediate layers
 Stratum Spinosum
 Stratum Granulosum
 Stratum Lucidum**
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Stratum Corneum (superficial)
Stratum Germinativum
(aka stratum basal)
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Newly synthesized keratinocytes attached to
basement by hemi-desmosomes
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Forms ridge contours at interface of epidermal
ridges and papillae of underlying dermis
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Ridge contours are developmentally
determined and visible in palmer, plantar, and
digits
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1 layer of Stem cells or germinative cells
dominate the stratum germintivum
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Undergoing mitosis
10-25% melanocytes, some merkel cells
Receives nourishment from dermis
Fingerprint Activity
Psoriasis
•Very common
between 15-35
•Autoimmune
disease
• increased rate of
mitosis despite
same rate of
shedding
•Non-contagious
•Treated w/topically
or phototherapy
Intermediate Strata
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Stratum Spinosum
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spiny or prickly layer
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Newly synthesized
keratinocytes (several layers)
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Cells continue to divide
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Langerhans cells abundant
Stratum Granulosum
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3-5 flattened grainy cell layers
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Stopped dividing, nuclei 7
organelles break down
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Produce keratin (durable,
water resistant protein)
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Produce glycolipids –reduces
water loss
Stratum Lucidum
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Thin layer clear layer
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Found in thick skin Densely
packed cells filled with keratin
Stratum Corneum
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Most Superficial layer
¾ of epidermis
20-30 layers of flat dead
keratinized or cornified
cells
Held tightly together by
desmosomes
Relatively dry (prevents
microorganism growth)
Lasts about 2 weeks
before shed
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Avg person sheds 40lbs of
skin in a lifetime!
Pigmentation:
Skin Color
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Melanin (yellow, brown or black
pigment)
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Freckles & moles are areas of heavy melanin
production
Carotene (orange-yellow pigment)
Converted to vitamin A for epithelial
maintenance
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Accumulates in stratum corneum
Dermal Circulation
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Oxygenated Hemoglobin - reddish tint
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Constricted blood vessels – pale
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Cyanosis – Sustained constriction bluish
color in Caucasian, only visible in nail
beds of dark skin
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Produced by melanocytes in epidermis
Production increases in response to sun
exposure
Prevents skin damage by absorbing UV
rays
All humans have same number of
melanocytes
What
causes the
appearance
of wrinkled,
leathery
skin?
Sun Exposure
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UV stimulates production of vitamin D3
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D3 is modified by liver and converted to calcitrol by
kidneys
Calcitrol essential for absorption of calcium and
phosphorus
Too much UV clumps elastin fibers causing
leathery appearance
UV destroys folate needed for DNA
synthesis
Too much UV can also cause chromosomal
damage in stem cells of stratum
germinativum causing skin cancer
Skin Cancer
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Most common form of cancer (and most preventable)
Basal Cell Carcinoma – originates in stratum
germanitivum
Squamous Cell Carcinomas – superficial layers
Malignant Melanomas
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Extremely dangerous
Begins as a mole
Melanocytes grow rapidly and metastasize through lymphatic
system
Know the
ABCD
rule!
Do Now: What are Stretch
Marks?
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Damage to the dermis (collagen & elastin
fibers) due to rapid stretching of the skin due
to rapid growth or weight gain
Appear reddish- purple at first then fade to a
lighter color over time
Tend to occur in regions of the body where
fat is stored
Hormonal changes, genetics, and diet can
all affect development of stretch marks
Dermis “hide”
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Dermis – contains network of blood
vessels, lymph vessels, and nerve fibers
Papillary Layer (thin superficial)
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Loose connective tissue
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Dermal Papillae indent epidermis
Supports and nourishes epidermis
Capillaries and nerves
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Meissners corpsucles – touch receptors
Reticular Layer (80% of dermis)
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fibroblasts., macrphages, mast cells
Meshwork of dense irregular connective
tissue
Elastic fibers provide stretch & recoil
Collagen fibers provide rigidity & strength
BV, sweat and oil glands
Phagocytes
Striae – stretch marks
Blisters
Cutis hyperelastica
Mechanoreceptors of Skin
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Merkel’s disk
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Meissner Corpuscle
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Pain
Chemicals
Ruffini’s ending
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Light Touch
Free Nerve Endings
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Skin Curvature
Heat
Stretch
Pacinian Corpuscle
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Deep Pressure
Vibrations
Sensory Homunculus
What causes a decubitus ulcer
or bed sore?
Caused by an interruption of blood
supply to a tissue causing
necrosis. These develop in
patients that have been bed ridden
for long periods of time. They are
caused by the weight of the body
on the skin overlying a bony area
compressing the blood supply.
Do Now: List & describe layers
of the Integument
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Epidermis
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Dermis
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Stratum corneum
Stratum lucidum
Stratum granulosum
Stratum spinosum
Stratum germanitivum (Basale)
Papillary Layer
Reticular Layer
Hypodermis
Subcutaneous Layer
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Not actually part of integument, blurred boundary
Anchors skin to muscles, but loosely so it can slide
Loose connective tissue with many adipocytes
Fat distribution changes as grow and mature
(shock absorption & insulation)
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Females thighs & breasts
Males abdomen “beer belly”
Contains no vital organs and few capillaries
Subcutaneous injection useful method of
administering drugs with hypodermic needle
Accessory Structures: Hair
and Hair Follicles
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2.5 million hairs on human body!!
Hair Growth Cycle
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Hair grows for 2-5 years about .3mm per day
then pushed to surface to be shed for new cycle
to begin (scalp 6-10 yr cycle, eyebrows 3-4
months)
Function
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Protect scalp from UV, cushion head, and
insulate skull
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Prevent entry of foreign particles in nostrils, ears,
and eyes
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Respond to stress or cold (arrector pili smooth
muscle in dermis forces hair to stand up)
Structure
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Walls of follicle contain cells of epidermis
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Hair Papilla – peg of connective tissue
containing capillaries and nerves, cell division
occurs
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Hair Root – anchors hair in to skin
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Hair Shaft – 3 layers of dead keratinized cells
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Medulla – core of hair (soft keratin)
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Absent in fine hair
Cortex – surrounds medulla (hard keratin)
Cuticle – surface single layer made of
overlapping shingles of cells
Hair Texture
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Oval – silky & wavy
Flat & ribbonlike – curly
Round – straight
Conditioners – smooth out rough
cuticles making it shiny
Split ends – cuticle wears away at
ends
Hair Types:
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Cuticle
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Coronal
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Crown like (stacked paper cups)
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Small rodents & bats
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Spinous
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Petal or triangular shaped
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Mink, cats and seals
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Imbricate
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Flattened, overlapping scales
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Humans and other animals
Medulla
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Fragmentary (trace)
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Discontinuous (broken)
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Continuous
Cortex
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Human pigment granules distributed by cuticle (except red-hair)
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Cattle, dogs and some humans have ovoid bodies
Human Hairs vs. Animals
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Consistent color & pigmentation throughout shaft (see
banding in animals)
Animal pigmentation is centrally located
Humans 2 types of hair:
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Vellus hair – fine body hair
Terminal hair – coarser, darker hair (increased testosterone
increases growth)
Hair Color
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Genetically determined
by type and amount of
pigment produced by
melanocytes
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Brown – true melanin
Blond - sulfur
Red - iron
Gray - Pigment
production decreases
White air bubbles within
hair shaft
Do Now: What is alopecia?
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Hairs not replaced as fast as they are
shed, begins anteriorly and progresses
posteriorly
Male pattern baldness – sex linked
trait by delayed action gene that when
turned on changes response to
testosterone
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Until recently, only cure inhibits
testosterone production
What are comedones?
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Acne is caused by blocked sebaceous duct, forming a
sebum plug
Affects over 85% of adolescents and young adults.
Secretions accumulate causing inflammation and possible
bacteria infection
Blackheads – open comedones, melanin oxidizes turning
black
Whiteheads – closed comedones
Hormonal changes can cause increased oil production
Try not to squeeze, scratch, pick, or rub the pimples.
Although it might be tempting to do this, it can lead to skin
infections and scarring.
Accessory Organs: Nails
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Protect exposed finger tips and limit
distortion when exposed to
mechanical stress
Tools – pick up or scratch itch
Free Edge
Nail body – dead keratinized cells
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Nail bed – epidermis covered by
nail body
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Nail root – anchors nail body
Nail matrix – nail growth occurs
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Cuticle – portion of stratum
corneum extending over nail
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Lunula – pale crescent (area of
obscured blood vessels)
Accessory Structures:
Sebaceous Glands
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Holocrine oil glands
Arrector pili muscle contracts squeezes the sebaceous gland forcing
oily secretion out
Sebum (oily secretion) lubricates hair and skin and inhibits bacteria
growth, slows water loss from skin
Glands are sensitive to androgens (sex hormones)
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Cradle Cap – overactive sebaceous glands
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Accessory Structures:
Sudoriferous (sweat) Glands
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About 3 million per person!
Merocrine (eccrine) Sweat Glands
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Secreted directly onto surface of skin via
exocytosis
99% water w/electrolytes, vitamin C,
antibodies, metabolic wastes and drugs, pH of
4-6
Cools surface of skin and lowers body temp
Too much perspiration may lead to dehydration
Flushes microorganisms from surface
Apocrine Sweat Glands
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sweat glands that secrete products into hair
follicles in armpits, nipples, and groin
Sticky, cloudy secretion released at puberty
Odorous as bacteria break it down as food
Slides of Scalp vs. Palm
Injury and Repair of Skin
Inflammatory response – triggered by mast cells increase blood flow to area
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Scab (fibrin proteins) forms at surface to restrict entry of microorganisms
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Cells divide rapidly to replace missing cells
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Macrophages and phagocytes clear debris and patrol area for pathogens
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Animation: http://www.youtube.com/watch?v=QHzHc9E8kTw&feature=related
Deeper wounds
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Scar tissue – lots of collagen fibers and few blood vessels
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Fetuses don’t scar
Keloid – thickened area of scar tissue with shiny smooth surface (tend to form in
adults with dark skin)
Damaged hair follicles, sebaceous and sweat glands, muscle cells and nerves
are rarely repaired
Burns
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1st degree – kills superficial epidermal cells, injures papillary dermis
2nd degree – kills epidermis and possible some dermis, injures reticular dermis
3rd degree – kills all epidermal and dermal cells, injures hypodermis and deeper
tissues
Skin Gun: http://www.youtube.com/watch?v=eXO_ApjKPaI
Aging
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Epidermis thins as stem cell activity decreases
increasing skin injuries and infections
Number of macrophages and other immune system
cells decreases
Decline in vitamin D3 production reduces calcium and
phosphorus absorption weakening muscles and bones
Melanocyte activity decreases causing increases
sensitivity to sun
Gland activity decreases causing dry scaly skin
Follicles decrease function creating thin light hair
Elastic fibers decrease resulting in wrinkling
Reduced blood supply to dermis – less
thermoregulation
Repairs are slow…6-8 weeks
Write an analogy for our skin….
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Human skin is like __________
because _______________.
Skeletal
System
Complete web
showing how
Integumentary
system
interconnected
w/other organ
systems!
Reproductive
System
Muscular
System
Nervous
System
Urinary System
Integumentary
System
Digestive
System
Endocrine
System
Respiratory
System
Cardiovascular
System
Lymphatic
System